1. Field of the Invention
This invention relates to an improved method and apparatus for producing tooth movement in the treatment of dental malocclusions.
2. Description of the Related Art
Conventional orthodontic techniques include edgewise and Begg. It is recognized that the Begg bracket is very similar to the pin and tube appliance introduced by Dr. Angle in 1910, but is inverted. In 1925, Dr. Angle removed the vertical pin slot from the bracket and cut an archwire slot in its face and added an extension (wing) to its gingival portion. This resulted in three dimensional tooth control. Dr. Angle saw limitations of his new edgewise bracket and suggested placing brackets at angles so that the insertion of straight archwires would tip the crowns. This concept eventually led to the development of the "straight wire" brackets that have torque and uprighting built into the archwire slots as well as in some instances rotational forces and labial lingual forces.
Straight wire brackets have the disadvantage that torquing, up-righting and rotation built into these brackets cannot satisfy the requirements for the correct final position of all teeth. The teeth in some instances may be over-torqued, up-righted over-rotated or placed too far lingually or buccally. In other instances, built-in torquing, up-righting or rotation angulations or other tooth movements of the straight wire brackets are less than needed. In both of the above situations, the orthodontist is required to use auxiliaries such as torquing wires, up-righting springs, place bends in the archwires or, lastly, change the entire bracket and replace it with a bracket having the necessary angulations for the final precise and correct placement of the teeth.
U.S. Pat. No. 3,408,739 describes a modification of the Begg technique including a vertically extending archwire slot which allows free tipping of teeth during treatment as compared to the edgewise brackets. Edgewise brackets have been described which provide tipping means when force is applied, as shown in U.S. Pat. Nos.: 4,842,512; 4,859,179; and 4,877,398. U.S. Pat. Nos. 4,227,876 and 4,242,085 disclose combination brackets having both labially or horizontally facing horizontal archwire slots and gingivally facing vertical archwire slots. In addition, U.S. Pat. No. 4,427,381 describes converting a Begg bracket into an edgewise bracket by the addition of attachments.
The brackets previously described have the disadvantage that they do not always function as desired. Also, the brackets are often cumbersome and unesthetic. In addition, it is necessary for the orthodontist to have a large inventory of brackets and many archwire changes for correction of dental malocclusions which is costly in both time and money to the orthodontist and oftentimes causes discomfort to the patient.
U.S. Pat. Nos. 4,799,882 and 5,098,288 describe brackets which have an improved esthetic appearance by using porcelain or plastic or in combination.
U.S. Pat. No. 4,303,532 describes using metal inserts in plastic brackets in order to overcome deformation of the plastic brackets when orthodontic forces are applied. These protective metal liners make the bracket larger and more unesthetic as the archwire is inserted from the labial surface and is clearly visible as is the metal liner.
Of possible general relevance to the invention are U.S. Pat. Nos.: 4,209,906; 4,268,249; 4,522,590; 4,523,908; 4,634,662 and 4,712,999 describing means for holding the archwire in place.